Tennis ball
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A tennis ball is the bouncing ball designed for the sport of tennis.
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[edit] Tennis balls in history
[edit] History
Tennis balls in the early days of tennis were often made of leather stuffed with hair or wool. Early tennis balls were made by the esteemed Scottish craftsmen. These tennis balls were commonly made from a wool-wrapped stomach of a sheep or goat and tied with rope. Those recovered from the hammer-beam roof of Westminster Hall during a period of recent restoration were found to have been manufactered from a combination of putty and human hair, and were dated to the reign of King Henry VIII. In the 18th century, ¾" strips of wool were wound tightly around a nucleus made by rolling a number of strips into a little ball. String was then tied in many directions around the ball and a white cloth covering sewn around the ball. This type of ball, but with a cork core, is still used for the original game of tennis, today called real tennis. With the introduction of lawn tennis in the 1870s, vulcanized rubber was first used to manufacture balls often in tubes of four with a package with the name of the brand.
[edit] Modern tennis ball construction
[edit] Appearance
The ball shall have a uniform outer surface. If there are any seams, they are stitch less.
Colour:
The ball shall be GREENISH YELLOW.
Size:
The ball shall be more than two and a half inches (6.35cm.) and less than two and five-eighths inches (6.67cm.) in diameter.
Weight:
The ball can be more than two ounces (56.7 grams) and less than two and one-sixteenth ounces (58.5 grams).
Performance characteristics:
The ball shall have a bound of more than 53 inches (135cm.) and less than 58 inches (147cm.) when dropped 100 inches (254cm.) upon a concrete base. The ball shall have a forward deformation of more than .220 of an inch (.56cm.) and less than .290 of an inch (.74cm.) and a return deformation of more than .315 of an inch (.80cm.) and less than .425 of an inch (1.08cm.) at 18 lb. (8.165kg.) load. The two deformation figures shall be the averages of three individual readings along three axes of the ball and no two individual readings shall differ by more than .030 of an inch (.08cm.) in each case.
[edit] Composition
The modern tennis ball comprises two major parts, the inner core and the outer cloth covering. The inner core is constructed of two half-shell pieces of formed rubber, which are joined together with adhesive to form a single core. Two dumbbell shaped pieces of cloth are attached to the ball core by adhesive to give the tennis ball its classic appearance. The thickness and density of the ball cloth is matched to the court type for which the ball is designed.
The balls currently in use can be subdivided into two categories:
- Pressurized balls have a core pressurised with air or nitrogen. These balls lose their pressure, and hence playing properties, over time.
- Non-pressurised balls are made from a thicker rubber core, and the pressure within the core is equal to the ambient pressure. These balls tend to hold their playing characteristics for a longer period of time, as it is only the cloth that deteriorates. Most players feel no difference between pressurized and pressureless balls, but top-level players claim a notable difference and thus prefer the former.
In 1999, the International Tennis Federation (ITF) approved an experiment in which two new types of tennis ball would be permitted for use in tournaments. The two types of ball were designed to have different performance characteristics derived from their differing dynamic and aerodynamic properties. With the introduction of the two new types of tennis balls (type I and III) there are now three types of ball available for play, type I, II and III. The ball construction for all three ball types can be either pressurised or pressureless as they are classified through measurement of the diameter of the ball and a compression test, which measures the forward and return deformation of the ball under an applied load. Type I balls are harder than the traditional type II balls and are designed for slow pace courts such as clay. Type III balls are larger in diameter by approximately 6-8%. Research shows that they are slower through the air due to their increased drag properties, and in addition have a steeper rebound angle both giving more time for the receiver to collect the ball. Larger balls have been requested in order to create a more 'watchable' game for the audience; due to the speeds, causing lack of visibility, that professional tennis players can now place on the ball.
Current regulations imposed by the ITF restrict the color of the ball to yellow or white and the seams of the tennis ball must be stitchless. Strict limits are also in place for the mass and diameter for each type of tennis ball, and in addition quasi-static tests are used to determine the ball's static stiffness and coefficient of restitution (COR) through a rebound test. Whilst these tests have the advantage of simplicity, (the rebound test was introduced in 1925 and has remained unchanged since) they may not represent how a ball performs under actual playing conditions. Incident ball speeds in the rebound test of 7m/s are far short of those found at the top echelons of the male game.
Older tennis balls were even black, depending on the color of the court. Green is not a mass produced color for tennis balls.[citation needed]
[edit] Safety Issues
Even though, as the name suggests, the ball is used primarily in tennis, it can be used as a safe substitute for games where a solid ball is necessary, for example, to replace a cricket ball, which can inflict damage or injury if not used correctly.
An incident in Oregon revealed that tennis balls are often used to make makeshift bombs. According to Snopes,
"On 25 November 2000, in Portland, Oregon, a chocolate-colored Labrador named Ivy was killed by an exploding tennis ball."
Tennis ball bombs of this nature are relatively common, and are typically abandoned by their makers when they do not detonate. According to the Snopes entry, abandoned tennis balls are best left alone, especially if surrounded with tape.
[edit] Tennis balls in literature
The gift of tennis balls offered to Henry in Shakespeare's Henry V is portrayed as the final insult which re-ignites the Hundred Years' War between England and France.
- When we have match'd our rackets to these balls,
- We will, in France, by God's grace, play a set
John Webster, The Duchess of Malfi
- We are merely the stars' tennis balls, struck and banded
- Which way please them
